Morning Glories will do just fine in large containers. Use commercial potting soil rather than regular garden soil, and check them daily during the warm weather to make sure the soil doesn't dry out. You may want to feed them every three weeks with a diluted liquid fertilizer. Since containers dry out quickly they are watered more often, which leaches the minerals out of the soil at a pretty fast pace. By feeding every three weeks you'll ensure that the plants get the nutrients they need. Enjoy!